1. Field of the Invention
The present invention relates to a method for producing a superconducting coil, and more particularly, to a method for producing a superconducting coil having no support member in its inside, that is, a so-called inner-bobbinless coil.
Recently, in view of various usages of coils, there has been a demand for a so-called inner-bobbinless coil that has no support member in its inside as a superconducting coil.
For instance, in colliding beam experiments of elementary particles, a particle's energy is to be measured for the purpose of specifying a new particle produced by collision of particles at an outside of a large size solenoid coil which is used as a target against which the particles collide. For this reason, it is necessary that the reduction amount of the new particle's energy reduction be minimized. It is therefore necessary that a thickness of a substance such as a coil through which the new particle passes be at a minimum. Accordingly, an inner-bobbinless coil that has no bobbin in its inside has been employed.
2. Description of the Prior Art
FIGS. 1 and 2 show a superconducting coil of the above-described inner-bobbinless type. In FIGS. 1 and 2, the superconducting coil 1 constitutes a coil which is produced winding by a predetermined number of turns of a conductive member whereby a superconducting member may be achieved. A support cylinder 2 supports the superconducting coil 1. In the coil of this type, as described above, it is necessary that the thickness of the part through which elementary particles pass be kept at a minimum and it is difficult to measure the energy of the particles. Therefore, it is impossible to apply a direct cooling method in which the coil is made to dip into liquefied helium contained in a container. Instead, an indirect cooling method is adopted in which a coil cooling tube 3, which serves as a flow passage for the liquefied helium, is provided in contact with an outer periphery of the support cylinder 2. In this way the coil is indirectly cooled through heat conduction by the liquefied helium flowing through the coil cooling tube 3.
Conventionally, there has been employed a method for producing such a coil as shown in FIG. 2. More specifically, in producing the superconducting coil 1 by winding the superconducting member, the superconducting coil 1 is arranged coaxially with and spaced at a predetermined interval apart from the support cylinder 2 supporting the coil. A resin or filler containing resin 4 is filled in the clearance therebetween so that the superconducting coil 1 is integrally formed with the support cylinder 2. Thus, the superconducting coil of the inner-bobbinless type is produced.
However, in the superconducting coil produced in accordance with the conventional method, there is a fear that the resin layer would be peeled off from the coil side or the support cylinder side upon curing of resin after the vacuum filling or upon the activation of the coil thereby decreasing the thermal conductance between the coil and the liquefied helium. This would be a problem in cooling ability of the coil. Furthermore, there is a fear that air would be mixed into the resin layer to remain as voids. This would also reduce the thermal conductance. Moreover, in case of a coil having a very large physical size such as a superconducting coil for experiments of elementary particles, it is necessary that in view of the workability of filling the resin, the clearance between the coil and the support cylinder be kept large to increase the thickness of the resin layer. The thermal conductance at the resin layer is low, which is a serious problem in cooling ability of the superconducting coil.